Left with a new bird seeing light (7)
I believe the answer is:
Here is my best explanation:
'light' is the definition.
(lantern is a kind of light)
'left with a new bird' is the subsidiary indication.
'left' becomes 'l' (common abbreviation).
'with' says to put letters next to each other.
'a new' becomes 'an' (I've seen this in other clues).
'bird' becomes 'tern' (tern is a kind of bird**).
'seeing' is the link.
(Other definitions for lantern that I've seen before include "Lamp with protective transparent casing", "Case for a portable lamp", "Light in a transparent protective case", "Light held by 26/27 Across", "Portable lamp case", "Case for holding a light", "Leading light", "Light-admitting structure on roof", "Enclosed light" and "outside D [DECORATION]".)